PFPortChecker 1.0

This port test uses a local application to listen for the server trying to connect and the positively verifies that your port is forwarded.
Most online port checks assume that you already have an application (such as your game or torrent) listening for the port test on your computer, and then assume that the test was OK simply because they were able to connect to your computer.

Also, web only port checkers are not able to test UDP since UDP is a connectionless protocol and there is no way to know if the packet actually made it to your computer without some sort of program on your computer waiting for that packet.